Quantification and identification of sperm subpopulations using computer-aided sperm analysis and species-specific cut-off values for swimming speed

Abstract

Motility is an essential characteristic of all flagellated spermatozoa and assessment of this parameter is one criterion for most semen or sperm evaluations. Computer-aided sperm analysis (CASA) can be used to measure sperm motility more objectively and accurately than manual methods, provided that analysis techniques are standardized. Previous studies have shown that evaluation of sperm subpopulations is more important than analyzing the total motile sperm population alone. We developed a quantitative method to determine cut-off values for swimming speed to identify three sperm subpopulations. We used the Sperm Class Analyzer^® (SCA) CASA system to assess the total percentage of motile spermatozoa in a sperm preparation as well as the percentages of rapid, medium and slow swimming spermatozoa for six mammalian species. Curvilinear velocity (VCL) cut-off values were adjusted manually for each species to include 80% rapid, 15% medium and 5% slow swimming spermatozoa. Our results indicate that the same VCL intervals cannot be used for all species to classify spermatozoa according to swimming speed. After VCL intervals were adjusted for each species, three unique sperm subpopulations could be identified. The effects of medical treatments on sperm motility become apparent in changes in the distribution of spermatozoa among the three swimming speed classes.

Key words::

• CASA
• curvilinear velocity
• mammals
• sperm classification
• sperm motility

Acknowledgments

The authors are grateful to Ms Charon de Villiers and colleagues, MRC Delft Animal Centre; Dr. Jürgen Seier and colleagues, MRC Primate Unit; Prof. Stefan du Plessis and postgraduate students, Reproductive Research Laboratory, Division of Medical Physiology, Department of Biomedical Sciences, Stellenbosch University; Prof. Schalk Cloete; Ms Annelie Kruger and colleagues, Elsenburg Experimental Farm for their assistance during collection of semen samples. This study was supported by the National Research Foundation (NRF) and Senate Research Fund of the University of the Western Cape.

Declaration of interest: GvdH collaborates with Microptic SL (Barcelona, Spain), the company from which the SCA^® system was purchased. For our research, the SCA^® system was employed solely as a research tool to define sperm subpopulations. Any opinion, findings, conclusions and recommendations expressed in this article are those of the authors; the NRF accepts no liability with regard to this report.